There are multiple ways to do this. The most simple is to use the Shell API and query for the System.Photo.CameraModel property, something like this:

#include <windows.h>
#include <shobjidl_core.h>
#include <propkey.h>
#include <stdio.h>

int main()
{
    CoInitialize(NULL);
    IShellItem2* item;
    if (SUCCEEDED(SHCreateItemFromParsingName(L"c:\\path\\photo.jpg", NULL, IID_PPV_ARGS(&item))))
    {
        LPWSTR str;
        if (SUCCEEDED(item->GetString(PKEY_Photo_CameraModel, &str)))
        {
            wprintf(L"Model: %s\n", str);
            CoTaskMemFree(str);
        }
        item->Release();
    }
    CoUninitialize();
    return 0;
}